1. Technical Field
Example embodiments of the present invention relate in general to the field of an antenna for a mobile communication base station, and more specifically to a dual polarization-based small antenna for a mobile communication base station.
2. Related Art
The mobile communication technology of today has been converted from an analog communication into a digital communication, and further evolved into 2G, 3G, and 4G. In particular, 3.9G services represented by LTE and WiMax are being introduced all over the world. As smart devices of a high performance, such as smartphones and tablets, are spread into public together with the development of the communication technology, the demand for a big data service such as high-definition multimedia is explosively increased, and thus a tremendous mobile traffic is expected in the near future.
For a paradigm of a mobile communication technology, advanced technologies, including an active phased array antenna technology, a multiple-input and multiple-output (MIMO) technology, and a beamforming technology, have been introduced and evolved as a method of increasing the data transmission speed and data transmission capacity to the utmost by using limited frequency resources.
However, the speed of development in the advanced technology does not catch up with the proliferation of the mobile traffic that increases by geometric progression. As a solution to the mobile traffic increasing due to the limited frequency resources and the commercialization of mobile communication technology, there is suggestion about gradually increasing the number of base stations. However, the suggested method of increasing the number of mobile communication base stations has drawbacks of increasing the energy consumption, the space required for base stations, and the maintenance cost for base stations in the position of a mobile operator, and therefore the method is found difficult to be converted into a new service that will be developed in the future.
A next generation mobile communication base station system needs to satisfy the demand for mobile traffics that increases by geometric progression based on the current system, and also needs to quickly respond to a new communication market that is to be developed in the future. The current mobile communication base station has a system configuration thereof changed such that an RF unit is separated from a base band unit and an antenna is provided adjacent to the RF unit to minimize the cable loss between the antenna and the system, thereby minimizing the power consumption and expanding the coverage and thus compensating for the constraints with the increasing mobile traffic.
Meanwhile, the mobile communication base station system has an architecture in which a Radio Frequency Unit (RFU), a Base Band Unit (BBU), and a Transport layer are located in one cabinet and connected to a transmission/reception antenna through a coaxial line. However, in the recent years, the mobile communication base station system has been developed in the form of a distributed base station in which a centralized station collected with a plurality of Digital Units (DUs) is separated from a Radio Unit (RU) referred to as a Remote Radio Unit (RRH), and the centralized station is connected to the RRH by using an optical line. That is, the next generation mobile communication base station is provided such that an RF unit separately provided from a baseband unit is connected to the baseband unit through an optical line, and then made adjacent to an antenna, in which the RF unit is provided in a compact structure and integrated into an antenna construction.
In order to achieve miniaturization of the compact RF unit in the next generation mobile communication base station system, the antenna needs to be reduced in size. That is, the reducing of the next generation mobile communication base station in size is determined by the miniaturization of the antenna, that is, a device taking the largest volume among single RF devices in the next generation mobile communication base station. However, the antenna used in the current base station has a significantly large size, and provided as an array antenna having a plurality of antennas in a single construction, therefore such an antenna has a difficulty in application to the next generation mobile communication base station.